McCook Lake is an oxbow lake, formed when the Missouri River changed course in the 19th century. The lake was named for General John Cook who commanded a company of soldiers stationed there in 1864. It is unknown when or why the "Mc" was added. During the 1930's, locks were constructed at each end of the lake. These locks were intended to allow the Missouri River to flow into the lake during periods of high flow in an effort to stabilize the lake level. Since construction of the main dams on the Missouri River, high flows on the river have been eliminated. In addition, the Missouri River was channeled in the 1950's and it has dug deeper into the ground and is now deeper than the lake itself, rendering the locks ineffective.
Without a source of water, McCook Lake would have shrunk to a muddy marsh filled with reeds years ago. For the past 50 years, local organizations have used various means to pump water into the lake to allow continued recreational use.
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